Stabilizing system using an amplidyne



Patented July 29, 1 952 STABILIZING SYSTEM USING AN AMPLIDYNE Edward P. Ney, Minneapolis, Minn, Frank L.

Hereford, Jr.,

Swarthrnore, Pa.,

Walter D.

Whitehead, Jru, Old Church, Va., and Alden R. Kuhlthau, Durham, N. H., assignors to the United States of America as represented by the Secretary of the Navy Application March 4, 1949, Serial N 0. 79,664.

3 Claims.

r The present invention relates to a stabilization system which makes use of the amplidyne.

More specifically, it relates to apparatus including an amplidyne whereby devices, such as un turrets, installed on a rolling or pitching support, a ship, for example, may be kept steady indirection.

The stabilization system consists essentially of a free gyroscope, an amplidyne, a control circuit for the same, a direct currentmotorand a gear train.

I The primary object of the invention is to stabilize a gun director against rolland pitch. An additional object is to provideadevice whereby the operator may control the motion of the director by a simple movement of a joystick, instead of manually moving the entire stand, thus relieving the operator of manual labor and allowing him to concentrate his efforts and attention on the more vital features of his work. A further object is to provide means whereby automatic tracking of the target is made possible.

Other objects and many of the attendant advantages of thisfiinvention will be appreciated readily as the same becomes understood by reference to the following detailed description, when considered in connection with the accompanying drawing, the single figure of which illustrates the .circuits and electrical apparatus. involved in a preferred embodiment thereof.

The stabilization signals originate in a gyroscope, not shown, having two pickoff coils I, which are connected in series-opposition, or bucking relationship, to the conductors 2 and 3,, which feed the output of said coils to the primary winding 4 of a transformer 5. It will be understood that the pickoif coils are traversed by alternating magnetic flux and are connected tozthe gyroscope to be moved in their own plane while in said flux, so as to vary the voltages induced therein, as they move to include more or less of said flux.

, There is introduced into the circuit a damping signal, here shown as a signal for an induction generator 56 of the Kollsman type whose output is connected to the terminals of the resistor l, which acts as a voltage divider by reason of the movable contact 3, so that any desired portion of the said generator voltage may be put in series with the pickoif coils l and winding 4, however, in such direction as to oppose the residual output from the coils I. This Kollsman generator 56 is driven by the motor 9 which operates the turret to be stabilized.

The output winding ID of the transformer is itor 23 complete the center-tapped, shown, and connected through wires ll, lzgand :3 to the cathodes andgridsof a duplex triode, here shown as the-tube M which maybe of type-5N7. A resistor 15 is interposed inlead l2, and may be of the order of 2,000 ohms. The anodes oithe tube It are connected through wires IE and I? to the ends or the center-tapped primary Winding iii of ,a transformer 26, the said center tap being connected to the positive end of the power supply through the wire I9.

The power supply is relatively simple, and cornprises a transformer 21 energized from volt mains, and having the customary secondary windings to supply electricity to tube filaments and heaters, as well as the high voltage energy for the anode circuits. The rectifier "2 2 suitably maybe of the type 523. A choke 2i] and a capacpower supply, which need not be well-filteredinasmuch as it is not used for the reproduction of sound.

The secondary winding 2,5:of the transformer is likewise center-tapped. The center tap is connected by a conductor .2"! to the cathodes of a pair of tubes 218 and-23, indicated'as-type 6L6, through the resistor 36, here 1,000 ohms, and

transformer winding 3!. The outer terminals of p the winding 25. are connectedthrough wires 32 and '33 to thecontrol grids of, tubes 28 and 29. In one of these wires, for example wire 3 2, two resistors .35 .and .35, each of the order of 5,006 ohms, are connected in series asshown, for a purpose to be described later.

The transformer, 3i introduces into the common grid circuit of tubes 28 and 28am alternating voltage of the order of magnitude or 50 volts. Thisyoltage increases or decreases the voltage applied to the respective grids of tubes 28 and 29 accordingly as the voltage across the secondary winding 25 of the interstage transformer 26 changes phase. This renders the current through the amplidyne fields M and 42 a phase-sensitive direct current.

The screen grids of the tubes 23 and 29. are connected by the wire 31 containing three resistors in series, here each, of the order of 25,000 ohms. The middle resistor has a slider 34 coopcrating therewith as shown and connected by wire 38 to the terminal ,39 forming the center tap between two input windings of an amplidyne 50, mechanically driven by the shaft i a constant speed motor 13, and also to the wire 24 which leads to the positive conductor ll? of the power supply. The anodes of tubes 28 and 29 are connected to said terminal 39 through the respective fields 4i and 42 of the amplidyne 40,

by way of terminals 43 and 44 and wires 45 and 45. Each field is shunted by a 0.25 mi. capacitor as shown at 41 and 48.

The amplidyne is a highly specialized form of direct current generator, of the separately excited type. It has two pairs or sets of brushes, set 15 and i6 being in the normal commutation plane, the other brushes, l8 and 79, at right angles to said plane, in the electrical sense. The normal set of brushes is short circuited by conductor 11, the other delivers the electrical output of the generator, which must of course be driven mechanically.

The characteristic feature of such a generator is that even a small external field will produce strong currents in the short circuited armature windings, thus setting up an intense flux due to the armature reaction. This flux is electrically at right angles to the field flux and is known as cross flux. It becomes very intense when the brushes are short circuited because of the large currents that then fiow in the armature windings.

This cross-field in turn generates relatively great voltages between the brushes constituting the second set, which also constitute the output terminals of the generator. Thus a small change in the field excitation input current causes a large change in the output of the generator. However, if it were attempted to draw current from these brushes, the cross-field thereby generated would in turn oppose and annihilate the normal field. This is prevented by providing a suitably placed compensating field winding, traversed by the entire output current, like the series winding of a compounded generator.

Due to the fact that the amplidyne is separately excited, the output of the machine is not selfsustaining, but is a function of said excitation, an ceases when the latter fails. When driven at a substantially constant speed, the amplidyne thus may be used to provide a relatively great response to a small input current applied to its field winding. The power amplifications secured range from a few hundreds to several tens of thousands, according to the design of the machine.

In the present case, the output of the two 6L6 tubes, 28 and 29, furnishes the variable energization to field windings 4| and 42, and the amplidyne 40 generates, in response thereto, sufi'icient power to operate the main turret motor 9. It will be understood that the polarity of the voltage generated by the amplidyne depends upon its field polarity and this in turn, through the electronic amplifier system, depends on the direction of shift of the pickoif coils l, l.

Thus the gyroscope carrying said pickoff coils controls the operation of the main turret motor 9, as to both the direction and the speed of its rotation. It will be noted that motor 9 is also a separately excited machine, hence reverses its direction of rotation when the voltage applied to the armature changes its polarity.

The output of the amplidyne 40 is connected, through its compensating winding 74, to the motor 9 to operate the latter, and the terminals 80 and SI of the amplidyne are also connected, by means of conductors 52 and 53, to the corresponding terminals 50 and leading ultimately to the grids of the tube 54. The motor 9, which has its field 57 separately excited, as shown, drives the turret which is to be stabilized and also, through the mechanical connection indicated by the dashed line 55, operates the Kollsman induction generator 55. It will be understood that the line 55 does not necessarily mean a single shaft, but in fact the Kollsman generator is reduced in speed in the ratio of 1:288 by suitable gearing included in said mechanical connection 55. An alternating current is supplied at low voltage to the input field of the Kollsman generator, and the resulting alternating output delivered from its terminals is fed to the terminals of the resistor 1 one of whose ends is connected to the wire 3, already described. Under the conditions stated, the voltage produced by induction generator 55 will be proportional to the speed of motor 9, and its relative phase will be determined by the direction of rotation of said motor.

Through the wires 52 and 53 the voltage produced by amplidyne 40 is led to the grids of tube 54, through the variable resistor 58 having the adjustable contact 59, and the capacitor 60 in series. A voltage dividing resistor 6| is bridged across the wires 52 and 53 and has an adjustable contact 62 thereon, connected to the cathodes of the tube 54, which preferably is a duplex triode although, of course, two separate triodes could be used if desired.

An independent power supply is provided for tube 54, as an ungrounded circuit is required. This is provided by the transformer 63 energized from the mains, and feeding center-tapped high voltage from a secondary winding to the rectifier tube 64, here a 6X5. The filament or heater may be energized from an appropriate secondary winding on transformer 63 or on transformer M, as preferred. The smoothing means for the rectified voltage consists of the resistor 65, here 500 ohms, and two capacitors 66 and 61, each suitably being 15 mf. The high voltage direct current ouput has its negative terminal connected to the cathodes of tube 54 through the wire 68, while the positive terminal is connected to the anode circuit between the resistors 35 and 36, by means of wire 69, which has a variable resistance H of the order of 50,000 ohms with the adjustable contact 10, in series therein.

The operation is as follows:

Let it be assumed that pickoff coils I, l are shifted by the gyroscope, out of the neutral position say, into the position illustrated, by reason of tilting of the gun director, due to pitch or roll of the ship. This shift of the coils l, I will cause the lower one to have in an increased voltage induced therein by the A. C. field, whereas the opposing voltage induced in the upper one is correspondingly decreased.

There now is an alternating voltage between conductors 2 and 3, equal to the difference of the two voltages just mentioned, and having a phase relationship or polarity always determined by whichever pickoff coil voltage is the greater. In addition there is also the damping voltage between conductor 3 and the slider 8, which always opposes the voltage differential of the pickofl coils, regardless of its direction. This will be discussed later.

The voltage differential, thus decreased by the damping voltage, is applied to coil 4 of transformer 5, and duly amplified by the electronic tubes I4, 28 and 29 and the circuits associated therewith, with the final result that field 4| or 42 of the amplidyne 40 receives a unidirectional excitation from one or other of tubes 28 and 29, depending upon the relative polarity of the A. C. voltage applied to coil 4, and of a Value proportional to said voltage.

This excitation will cause the amplidyne to generate a much increased D. C. voltage of a relative polarity corresponding to that of the original differential -pickoifsignalfand of a relative pmagnitudelikewise corresponding to that of the delivered from its terminals 80 and 8|, supplies the power to drivetheturret motor 9,-which is responsive to polarity, said motor 9 will' o-perate --'in theproper direction to restore the turretto its desired-stabilized condition; and-at a-speedfcommensurate wi-ththe-extent off the error: from such condition. 4

' The 'Kollsman damping generatorifi meanwhile is providing a damping voltage proportional to the speed of the turret motor 9, and always of I such polarity as to oppose the pickofi differential voltage. This prevents overrunning, as the voltage fed to the motor 9 will begin to decrease before the said motor has finished its proper response, so that the effect of mechanical inertia is thus compensated.

The power supplies, based on tubes 22 and 64 respectively, are or may be conventional and need no further explanation.

The electronic tube 54 and its associated circuit have the purpose of preventing hunting. It will be noted that the grids of this tube are connected to the conductors 52 and 53 which lead to the motor 9. The capacitor 60 in the circuit prevents any current flow through resistors 58 and 6| so long as the D. C. voltage between conductors 52 and 53 remains constant, but permits transient flow whenever said voltage varies. The resultant grid voltage fluctuations will produce corresponding anode current pulses through resistors and 3B which in turn produce varying voltage drops therein, that are fed to the control grid of tube 28.

Due to the tremendous amplification between the pickoil coils l, i and the output of the amplidyne 49, instability would result at the normal zero setting of the pickoff coils, in response to slight parasitic disturbances. Such instability, which would otherwise cause hunting, is oifset by the compensating voltage pulses of the control grid of tube 23. Only one of the output tubes need be thus compensated, thus simplifying the circuit.

In order to preventany disturbance of the normal bias of the said control grid, however, the tube 54 is of the dual type, and the respective anode currents thereof flow in opposite directions through the resistors 35 and 36, to eliminate the voltage drops due to normal anode currents in tube 54. Adjustments are provided by the sliders 53 and '62, the former controlling the sensitivity of the circuit, the latter serving to balance out any inherent difierences in the two triodes constituting the tube 54.

It will now be understood that by means of the apparatus described herein, any disturbances of the normally level position of the gun-director support will immediately produce a signal from the free-gyro pickoii coils, which, after amplification, restores the support to its normal position by actuating the turret motor. Usually the whole system is provided in duplicate units, one unit correcting for roll, the other for pitch, but in other respects being substantially identical with one another. Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

l.-- ln adamping device iorastabilizingsystem,

comprising, direct current drive motoflsa gen- *-era tor for energizingsaid motor, a circuit connecti'ng theterminals or said motor and includ- --i-ng, in series, a variable resistor, *a capacitor and a "voltage-dividing -resistor having 1 an adjust-abIe'cOntact, apair oi triode sections, said sections having their cathodes connected to each other and to said-adjustablecontact,and having their respectivegrids connected to the terminals of said voltage-dividing resistor, a center-tapped resistor 'having its terminals connected to the respective anod'es-of-said pair of triode sections, a source of electricity having a negative terminal connected to said cathodes and having a positive terminal connected to the center tap of said last-named resistor to supply anode power to said triode sections, and a circuit introducing the voltage between the terminals of said last-named resistor into the field of said generator to control the output of said generator to said motor.

2. In a damping device for a stabilizing system, comprising, a direct current drive motor, an amplidyne generator for energizing such motor, a circuit connecting the terminals of said motor and including, in series, a variable resistor, a capacitor and a voltage-dividing resistor having an adjustable contact, a pair of triode sections, said sections having their cathodes connected to each other and to said adjustable contact, and having their respective grids connected to the terminals of said voltage-dividing resistor, a center-tapped resistor having its terminals connected to the respective anodes of said pair of triode sections, a source of electricity having a negative terminal connected to said cathodes and having a positive terminal connected to the center tap of said last-named resistor to supply anode power to said triode sections, and a circuit introducing the voltage between the terminals of said last-named resistor into the field of said amplidyne generator to control the output of said amplidyne generator to said motor.

3. A stabilization system for a movable element, comprising, a free gyroscope to provide an alternating current signal whenever the element deviates from its desired condition, said signal being phased to correspond to the sense of said deviation, means for providing a voltage opposing said signal, means for amplifying said signal and deriving therefrom a correspondingly polarized unidirectional current, an amplidyne, said amplidyne having its field excited by said current to generate a voltage of a relative polarity corresponding to that of said signal from said pickofi coil and of a magnitude corresponding to the signal input, a direct current motor energized by said amplidyne and operatively mechanically connected with the element to be stabilized, said motor being responsive to polarity so as to be operated in the proper direction to restore the element to its desired stabilized condition at a speed commensurate with the extent of error from such condition, means assisting in preventing hunting of the motor, said means including a circuit connecting the terminals of said motor and having, in series, a variable resistor, a capacitor and a voltage-dividing resistor having an adjustable contact, a pair of triode sections, said sections having their cathodes connected to each other and to said adjustable contact, and having their respective grids connected to the terminals of said voltagedividing resistor, a center-tapped resistor having 2,605,452 7 8 6 its terminals connected to the respective anodes REFERENCES CITED of mode source The following references are of record in the trlcity having a negative terminal connected to file of this patent:

said cathode and having a positive terminal connected to the center tap of said last-mentioned 5 UNITED STATES PATENTS resistor to supply anode power to said triode Number Name Date sections, and a circuit introducing the voltage be- Re. 16,667 Hewlett et a1. July 5, 1927 tween the terminals of said last-mentioned re- 1,679,354 Fairchild et a1. Aug. '7, 1928 sistor into the stabilization system to constitute 2,115,086 Riggs Apr. 26, 1938 a component of the control thereof. 10 2,432,302 Fisher Dec. 9, 1947 2,478,203 McCoy Aug. 9, 1949 DW R P-NE 2,481,550 White Sept. 12, 1949 FRANK L. HEREFORD, JR. WALTER D. WI'HTEHEAD, JR. ALDEN R. KUHL'I'HAU. 15 

